1. Field of the Invention
The present invention relates to an optical pickup device and more particularly to the configuration of an optical pickup device having two separate optical systems that are selectively used according to the type of optical disc.
2. Description of Related Art
Conventionally, optical pickup devices are used to read information on an optical disc and write information on the optical disc. There are a plurality of types of optical discs such as a compact disc (CD), a digital versatile disc (DVD) and a blue-ray disc (BD). Thus, for convenience and the like, among conventional optical pickup devices, there are some optical pickup devices that can be compatible with a plurality of types of optical discs.
Among the optical pickup devices compatible with a plurality of types of optical discs, there are some optical pickup devices which have two separate optical systems that are selectively used according to the type of optical disc (for example, see patent documents 1 and 2). Here, the optical systems each function to guide light emitted from a light source to the information storage surface of the optical disc and to guide the light reflected off the information storage surface to a light receiving element. As a specific example of these optical pickup devices, there is an optical pickup device in which one of the optical systems is used such as for reading information on a BD and in which the other optical system is used such as for reading information on a DVD or a CD.
Incidentally, in an optical pickup device, an objective lens for condensing light emitted from a light source on the information storage surface of an optical disc is mounted on an objective lens actuator. This objective lens actuator can move the objective lens mounted at least in a focus direction and in a track direction. Here, the term “focus direction” refers to a direction that is perpendicular to the information storage surface of the optical disc; the term “track direction” refers to a direction that is parallel to a radial direction of the optical disc. The purpose of moving the objective lens in the focus direction is to control (perform focus control) the focal position of the objective lens such that the focal position is constantly located on the information storage surface. The purpose of moving the objective lens in the track direction is to control (perform track control) a light spot obtained by condensing light through the objective lens such that the light spot constantly follows the track of the optical disc.
For example, as disclosed in patent document 1, among the optical pickup devices which have two separate optical systems, there are some optical pickup devices in which the optical systems individually include separate objective lens actuators (that is, include two actuators). However, in order to reduce the size of and the number of components of the device and the like, as disclosed in patent document 2, it is preferable to mount the objective lenses included in the optical systems on one lens holder and to move the two objective lenses with one objective lens actuator.
[Patent document 1] JP-A-H10-74328
[Patent document 2] JP-A-2006-202416